Microprocessors are increasingly used to control operation of the engine of an automotive vehicle or of other automotive vehicle components, such as, for example, braking, and/or clutching systems used therein. Microcomputers which are used in such vehicles work together with memories, usually programmable memories. Different vehicles which may require similar programming steps, for example to control the ignition instant of an automotive engine, may operate, however, based on different characteristic data. The characteristics of engine operation, for example relating ignition instant or ignition timing to engine temperature, loading and the like, vary with different engines, although the computation steps to compute the proper ignition instant based on the various characteristics are identical. Thus, it is possible to use a single microprocessor, programmed to carry out programming sequences with various types of engines or vehicles, provided the data on which the processor carries out its programs are matched to the respective engine or vehicle.
The referenced publication "Elektronik", No. 22, 1982, p. 143 et seq., describes an apparatus in which a microprocessor is connected to a serially operating interface which, in turn, is connected to a programmable memory. Data can be transmitted between the microcomputer and the memory via the serial interface. Data transmitted, for example, from the memory to the microprocessor are then processed in the microprocessor in accordance with its program. Flexibility of the system is ensured by using a memory in which the data, for example, can be changed.
U.S. Pat. No. 4,255,789, Hartford, describes a control system for a motor vehicle in which a microprocessor works together with a programmable memory. The memory is programmed, or has data entered thereinto before assembly with the operating control system. Change in a program is possible only, after incorporating the memory in the system, by replacing an integrated circuit element of the memory. Such change of the program is, however, desirable even after installation in the system, for example to compensate for effects of aging. In practical application, problems arise when utilizing a microprocessor with a preprogrammed memory. If the overall system is located within a sealed housing, change in the memory content can only be obtained by exchanging a memory integrated circuit (IC), or a group of memory ICs. This requires opening the housing, or other interference with its integrity, which may permit contamination of the contents of the computerized control system by dirt and/or dampness or humidity. Locating the memory IC on a plug-in base interferes with the integrity and operating reliability of the overall system since, in the environment of an automotive vehicle, plug-in connections of ICs are difficult to maintain in perfect contact due to the subjection to shock, vibration, changes in temperature, and the like, conditions endemic in operation of an automotive vehicle, although not necessarily encountered in office computer applications.
It has been proposed to provide programmable memories for use in combination with vehicular-type microprocessors, in which the programming or memory content to be stored in the memories can be carried out by external programming units, so that the read-only capability to be utilized by the microprocessor can be based on data specific to a particular type of engine, vehicle, or a specific use thereof. It is then possible to program the data within the memory, for example, to be particularly applicable to a specific engine, and/or customer requirements. For example, the data which can be stored in the memory may be idle speed, fuel/air mixture for use under idling, and the like. Programming for such conditions is best carried out during production of the vehicle, and/or at an installation stage when the vehicle is associated with a specific control unit, that is, during a mass-production run. Such programming during mass-production permits matching not only the data to be stored to a specific engine, but, additionally, for example to environmental conditions such as quality of fuel to be expected with which the vehicle is to be used, composition of fuel--for example whether containing alcohol or only hydrocarbons--use under tropical conditions and the like; changes due to production variations, for example within a production series, are likewise possible without exchange of the entire control unit. It is also not necessary to merely exchange a pre-programmed memory for another one, so that plug-in connectors for the memory units can be eliminated, thus substantially increasing the operating reliability of the overall control system.